Michael,

As you probably know, tin/lead/plated/fused solder termination areas "ruled" the earth before
commercial SMT. It was/is the most solderable surface available - in my objective opinion. Its
homogeneous surface is very nearly impervious to oxidation except under extreme conditions.

You are right about coplanarity as tin/lead/plated/fused pads have a huge "hump" in the middle, but
HASL is not working well in this department either - for fine pitch. If someone could come up with a
tin/lead/plated/fused process, not violating environmental issues and was flat, wouldn't it be
great?

Earl Moon

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